Greywater

Question 1

Describe dark vs light greywater

Answer 1

• Heavy/dark greywater
  o Dishwasher, kitchen tap, washing machine
  o Higher pollutant load
  o Higher heat discharged
• Light greywater
  o Shower, bathroom tap
  o Higher pathogen load
  o Lower heat discharged

Question 2

How much of the total WW is greywater?

Answer 2

• 50 – 80% of total wastewater

Question 3

What pollutants are found in greywater?

Answer 3

o Organic matter
 TOC, BOD, COD
 Reduces level of dissolved oxygen. Degrades aquatic life. Growth of microorganisms. Effects biodegradability.
o Phosphorus
 Eutrophication, excess algae and plant growth. Reduced levels of oxygen. Blocks sunlight. Degrades aquatic life.
o E.coli
o Chemicals
 Personal care products, detergents, soap etc, surfactants
 Pollutes soil and water. Helps colloids form. Clogs the system. Affects settling rate of particles. Contributes to microplastics and micropollutants
o Salts
 Boron, sodium, chloride
 Increases salinity. Affects plant growth. Soil and groundwater pollution.
o TSS
o Microplastics
o Entrococci
o Nitrogen/ammonium
 Eutrophication. Soil acidification.

Question 4

Name some intensive biological processes for treatment?

Answer 4

 Rotating biological contactors
 Sequencing Batch Reactors
 Aerobic Filters (trickling filter)
 Membrane Bio-reactor

Question 5

Name an extensive biological process and a nature-based solution for treatment?

Answer 5

o Extensive biological processes
 Constructed wetlands
o Nature-based solutions
 Constructed wetlands
 Living wall/Green wall

Question 6

Why should greywater be reused?

Answer 6

 Increasing global population
 Climate change
 Limited natural water resources
 90-94% water use in agriculture
 55% increase in global water demand by 2030

Question 7

What is the most frequently described characteristic of greywater?

Answer 7

The variability in volumes and concentrations

Question 8

What is intensive treatment?

Answer 8

Intensive biological processes aim to reduce the
required reactor size by intensifying the biological processes by either increasing
the concentration of retained biomass or increasing the rate of oxygen transfer.

Question 9

What is extensive treatment?

Answer 9

extensive processes operate in a
more passive manner such that they do not tend to use active aeration or mixing.

Question 10

How are pathogens treated?

Answer 10

Pathogen control in greywater systems is normally achieved through a combination
of removal across the main processes (e.g., MBR or reed bed) and final disinfection
with either chlorine or UV.